See Also: EnvironmentPermission Members
Environment variable names are designated by one or more case-insensitive name lists separated by semicolons, with separate lists for read and write access to the named variables. Write access includes the ability to create and delete environment variables as well as to change existing values.
In versions of the .NET Framework before the net_v40_long, you could use the System.Security.CodeAccessPermission.Deny method to prevent inadvertent access to system resources by trusted code. System.Security.CodeAccessPermission.Deny is now obsolete, and access to resources is now determined solely by the granted permission set for an assembly. To limit access to files, you must run partially trusted code in a sandbox and assign it permissions only to resources that the code is allowed to access. For information about running an application in a sandbox, see How To: Run Partially Trusted Code in a Sandbox.